#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <curl/curl.h>
 
/* Auxiliary function that waits on the socket. */
static int wait_on_socket(curl_socket_t sockfd, int for_recv, long timeout_ms)
{
  struct timeval tv;
  fd_set infd, outfd, errfd;
  int res;
 
  tv.tv_sec = timeout_ms / 1000;
  tv.tv_usec = (timeout_ms % 1000) * 1000;
 
  FD_ZERO(&infd);
  FD_ZERO(&outfd);
  FD_ZERO(&errfd);
 
  FD_SET(sockfd, &errfd); /* always check for error */
 
  if(for_recv) {
    FD_SET(sockfd, &infd);
  }
  else {
    FD_SET(sockfd, &outfd);
  }
 
  /* select() returns the number of signalled sockets or -1 */
  res = select((int)sockfd + 1, &infd, &outfd, &errfd, &tv);
  return res;
}
 
int main(void)
{
  CURL *curl;
  /* Minimalistic http request */
  const char *request = "GET / HTTP/1.0\r\nHost: example.com\r\n\r\n";
  size_t request_len = strlen(request);
 
  /* A general note of caution here: if you are using curl_easy_recv() or
     curl_easy_send() to implement HTTP or _any_ other protocol libcurl
     supports "natively", you are doing it wrong and you should stop.
 
     This example uses HTTP only to show how to use this API, it does not
     suggest that writing an application doing this is sensible.
  */
 
  curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    curl_socket_t sockfd;
    size_t nsent_total = 0;
 
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    /* Do not do the transfer - only connect to host */
    curl_easy_setopt(curl, CURLOPT_CONNECT_ONLY, 1L);
    res = curl_easy_perform(curl);
 
    if(res != CURLE_OK) {
      printf("Error: %s\n", curl_easy_strerror(res));
      return 1;
    }
 
    /* Extract the socket from the curl handle - we will need it for
       waiting. */
    res = curl_easy_getinfo(curl, CURLINFO_ACTIVESOCKET, &sockfd);
 
    if(res != CURLE_OK) {
      printf("Error: %s\n", curl_easy_strerror(res));
      return 1;
    }
 
    printf("Sending request.\n");
 
    do {
      /* Warning: This example program may loop indefinitely.
       * A production-quality program must define a timeout and exit this loop
       * as soon as the timeout has expired. */
      size_t nsent;
      do {
        nsent = 0;
        res = curl_easy_send(curl, request + nsent_total,
            request_len - nsent_total, &nsent);
        nsent_total += nsent;
 
        if(res == CURLE_AGAIN && !wait_on_socket(sockfd, 0, 60000L)) {
          printf("Error: timeout.\n");
          return 1;
        }
      } while(res == CURLE_AGAIN);
 
      if(res != CURLE_OK) {
        printf("Error: %s\n", curl_easy_strerror(res));
        return 1;
      }
 
      printf("Sent %lu bytes.\n", (unsigned long)nsent);
 
    } while(nsent_total < request_len);
 
    printf("Reading response.\n");
 
    for(;;) {
      /* Warning: This example program may loop indefinitely (see above). */
      char buf[1024];
      size_t nread;
      do {
        nread = 0;
        res = curl_easy_recv(curl, buf, sizeof(buf), &nread);
 
        if(res == CURLE_AGAIN && !wait_on_socket(sockfd, 1, 60000L)) {
          printf("Error: timeout.\n");
          return 1;
        }
      } while(res == CURLE_AGAIN);
 
      if(res != CURLE_OK) {
        printf("Error: %s\n", curl_easy_strerror(res));
        break;
      }
 
      if(nread == 0) {
        /* end of the response */
        break;
      }
 
      printf("Received %lu bytes.\n", (unsigned long)nread);
    }
 
    /* always cleanup */
    curl_easy_cleanup(curl);
  }
  return 0;
}